Multi-spindle machines are known in the prior art. Multi-spindle machines are used to mass produce standardized types of components. A multi-spindle machine typically has several work stations at which machining operations are performed. A piece of raw stock, such as a bar stock, enters the machine at a first station and as the machine indexes, various machining operations are performed. Once the station is indexed completely through the machine, a completed part is formed. The part is released, and the process is repeated for that station with a new piece of raw stock. An advantage of multi-spindle machines is that all stations in the machine can simultaneously contribute to producing parts, resulting in high production.
Multi-spindle machines (also referred to as multiple spindle machines) typically have a large indexing spindle drum with four, five, six or eight work spindles thereon. Each of the spindles carries a work piece. Generally in all but one of the stations, where a new piece of stock enters, a machining operation is performed. After each machining operation is completed, the drum is rotated so that each work piece moves sequentially through the locations where the various machining operations are performed. Machining operations that are typically performed at a multi-spindle machine include turning and threading. Most multi-spindle machines are very efficient in terms of producing standardized parts at a high rate.
Typically, the speed of multi-spindle machines changes from high to low speed and back again during the course of the operating cycle. High speed is normally used for times in the machine cycle when critical machining operations are not occurring. High speed operation is desirable when the drum is indexing, or when the tools are moving toward or away from the work pieces and are not performing work thereon. Low speed operation is generally used when the tools in the machine are cutting or forming the metal. An attempt to operate the machine at a high speed when such cutting or forming work is being performed is likely to cause a problem or jam the machine.
In many multi-spindle machines at the final station the machined work piece is cut off from the remaining stock. The machined work piece is often dropped onto a conveyor or other device to move it away from the machine. It is common to perform additional operations on the machined part before it is ready for use. These additional operations are often done by hand or in other machines and add substantial cost to making the part. In many machines the movement of the work piece after cut off is unpredictable and may result in nicks on the ejected work piece. Therefore, work pieces sometimes become damaged and unusable. Furthermore, because the work piece is released from a rotating collet, large work piece catchers are sometimes required in order to ensure catching and guiding of the falling work pieces. Additionally, the catchers often have to be situated in a crowded tool zone, which often makes it difficult to control the cut off part and avoid damage to parts and other machine components.
In some multi-spindle machines pick-off attachments are available for pick-off of work pieces in the station where the completed work piece is cut off from the remaining stock. The movement of a pick-off attachment is typically set with the timing of the multi-spindle machine. After the work piece is separated from the remaining stock by being cut off, the cut off area may be subject to back machining operations, such as chamfering. The pick-off and back machining operations are controlled by mechanical cams and actuating devices in the machine. A pick-off attachment can include a dead length collet type attached to a pick-off spindle. The collet may be operated by twin toggles controlled by a special cam mounted on the main camshaft in front of the main drive housing. The pick-off spindle collet is able to grip and release a work piece.
The operation of a pick-off spindle collet is known in the art. A pick-off collet can be axially driven by cams and levers to position the collet over the work piece held by the work spindle. The pick-off collet can grippingly engage the work piece which is then cut from the remaining stock. The piece may be rotated in the pick-off spindle and have a back machining operation performed thereon. An ejector plunger may be used for removal of the work piece from the pick-off spindle. The pick-off spindle can be axially retracted toward the stationary ejector plunger so that the work piece is pushed out of the pick-off collet by the ejector plunger.